A semiconductor device such as an integrated circuit has a plurality of electrodes projected from its device body. This type of semiconductor device is subjected to an electrical test, i.e., electrical characteristic test, by use of an electrical connecting apparatus called socket, as to whether or not it has a predetermined function. One of such electrical connecting apparatus is described, for example, in Patent Document 1.
[Patent Document 1] Japanese Patent Appln. Public Disclosure No. 2003-123874
The electrical connecting apparatus described in Patent Document 1 comprises: a plate-shaped housing to be assembled into a base plate which has a plurality of belt-like conductive portions such as part of wirings of a wiring pattern on the upside of an electrically insulating plate member; a plurality of plate-shaped contacts arranged in the housing in parallel to electrically connect the conductive portions of the base plate and the electrodes of the device under test; and a rod-shaped needle retainer i.e., needle presser disposed in the housing so as to extend in the arrangement direction of the contacts.
Such a connecting apparatus is attached to the upside of the base plate by a plurality of screw members screwed into the base plate such as a wiring board to penetrate the housing in its thickness direction.
The housing has a recess extending in a first direction within a horizontal plane and opening downward; a plurality of slits extending in a second direction orthogonal to the first direction at intervals in the first direction within a horizontal plane; and an opening which opens upward and downward and communicated at its lower end portion with the upper portions of the slits.
Each slit is communicated with the recess and the opening, respectively, at its rear end portion and front end portion in its longitudinal direction and opened at least downward.
Each contact includes a principal portion having a curved outer face and received in the recess and the slit of the housing so that the curved outer face may be directed to the conductive portion of the base plate; a front end portion continuous to the front end side of the principal portion and projecting from the slit into the opening of the housing so as to be pressed relatively against the electrode of the device under test; and a rear end portion continuous to the rear end side of the principal portion and located in the recess. The front end portion of each contact has an arc-shaped front end face extending in the second direction.
The needle retainer is made of a rubber material such as silicone rubber into a cylindrical shape and is disposed in the recess of the housing and made to abut a position opposite to the curved outer face of the contact so that a part of the curved outer face of the contact may be brought into contact with the conductive portion of the base plate.
Each contact has a part of the arc-shaped outer face abut the upside of the conductive portion of the base plate with the connecting apparatus assembled into the base plate and has its rear end face abut a rear-side inward face of the recess.
When the front end face of the front end portion of each contact and the electrode of the device under test is pressed relatively, an overdrive OD acts on the contact. Thereby, each contact, while compressing the needle retainer to elastically deform, angularly rolls over the upside of its conductive portion with the part of the curved outer face abutted on the conductive portion.
As a result, each contact scrapes away a part of an oxide film of the electrode of the device under test and electrically connects the electrode of the device under test to the conductive portion. In this state, a electrical test of the device under test is carried out.
In the above-mentioned electrical connecting apparatus, however, shavings resulted from scraping away a part of the oxide film of the electrode of the device under test are prone to accumulate in the front end face and its neighborhood of the contact. As a result, since the accumulated shavings, i.e., part of the oxide film are non-conductive, a contact resistance between the contact and the electrode becomes high, so that a correct electrical test cannot be conducted.
An experiment by the inventors of this application clarified that the foregoing is resulted because, in the conventional electrical connecting apparatus, an upward projecting dimension of the front end portion of the contact is small, and because the radius of curvature of the front end face is greater than the thickness of the plate-shaped contact.